This invention relates to expansion joints and, more particularly to composite expansion joints of the type employed in bridge deck constructions for accommodating large movements between adjacent deck sections. Composite expansion joints are conventionally used in those constructions, such as bridge structures and the like, wherein the relative movement between adjacent deck sections in response to temperature changes is too great to be accommodated by a single seal unit. These known composite expansion joints often consist of a series of laterally spaced elastic seals separated by rigid structural members or plates and extend lengthwise of the expansion groove between adjacent bridge deck sections. The rigid structural members or plates are in turn mounted above and on support bars which extend transversely of the expansion groove.
It is known to connect the structural members to support bars in view of the necessity to maintain intimate contact therebetween in view of impact and wheel loads imparted by vehicles passing thereover. When a vehicle traverses over such an expansion joint, the component members thereof are subjected to flexural bending. The rebounding movement due to this bending movement causes the component parts of the espansion joint to impact against one another thereby emitting noises and undergoing considerable "pounding" which deteriorates the joint over a period of time.
Presently, there are two methods by which structural members and support bars are kept in close contact. The first method generally includes the welding of the two components (support bar and structural member) together and providing clustered groups of support bars of multiple units corresponding to the number of structural members so that each structural member is welded to a separate support bar in each cluster and spans those support bars to which it is not welded. Such a structure is provided by designing the support bars to be welded to a structural member at a point one or more inches above the surface of adjacent support bars.
The second method of maintaining surface contact between structural members and support bars is by the use of an uplift restraint assembly which permits a structural member to slide along a support bar while being held in intimate contact therewith so that multiple structural members may be mounted on one support bar.
Although the above prior art structures have been satisfactory in operation, they have not included the flexibility of operation as afforded by the present invention. In designing an expansion joint device, it is desirable to provide for as free a movement of the parts therein as the design will permit and still operate satisfactorily. However, due to such environmental conditions as the sun rising in the east and setting in the west a bridge in many cases receives some sunlight on one side prior to receiving sunlight on the other side. This in turn causes expansion of the bridge to take place on the relatively warmer side at a greater rate than on the relatively cooler side. The resulting differential expansion accordingly causes one side of the expansion joint would be wider at one end (one side of the bridge) than at the other end of the joint (the other side of the bridge). A similar type of movement of the structural members could also take place when for example a braking vehicle passes over an extreme end portion thereof tending to skew the orientation of the structural member with respect to its normmal longitudinal disposition within the expansion groove. With a welded configuration it can be seen that stresses would be introduced at each of the support bar connections because of the skew movement of the structural members. Similar types of stresses would also be developed where the structural members are slideably mounted on the support bars by means of uplift restraints.